Microphone construction



Oct. 31, 1961 c. F. PAULL ETAL 3,007,013

MICROPHONE CONSTRUCTION Filed April 22, 1959 INV ENTORS CHARLES F. PAULL ROBERT H. CHORPENNING wW -M ATTORNEY United States Patent 3,007,013 MICROPHONE CONSTRUCTION Charles F. Pauli and Robert H. Chorpenning, Conneaut, Ohio, assignors to The Astatic Corporation, Conneaut, Ohio, a corporation of Ohio Filed Apr. 22, 1959, Ser. No. 808,244 13 Claims. (Cl. 179121) The present invention relates generally to the art of translating and transmitting sound and more particularly to an improved and highly simplified construction for microphones and the like.

As will be understood by those skilled in the art, a microphone is employed for translating sound waves into proportional electrical signals. By far the greater number of microphones presently employed are of a type which use a piezo-electric transducer element as the transducer means. The relatively low cost and high efiiciency of this type of microphone makes the same well adapted for use in large volume products, such as public address system-s, home recording apparatus, amateur radio broadcasting sets, etc. A second type of microphone which is also widely employed is that type operating on a variable resistance principal. A quantity of carbon granules serve as the transducer means which is operative to modulate a direct current potential. The variable rmistance type of microphone is widely employed in short wave, intercommunication and dispatching systems.

The teachings of the present invention will be described in connection with the two above mentioned types of microphones, but it should be understood from the outset that the teachings of the invention are equally applicable to other types of microphones.

Microphones constructed in accordance with the prior art are usually characterized bytheir complexity in manufacture and assembly and their large number of component parts. For example, in a piezoelectric type of microphone a multiplicity of rubber pads serve as mounts on which the transducer element is secured. These pads must be accurately controlled as to their various physical dimensions and properties, such as hardness and resiliency, and must be positioned in a housing with a reasonable degree of accuracy. This necessitates rigid quality control programs and entails the use of rather complicated locating jigs. The piezoelectric transducer element must be accurately located on and cemented to certain of the pads and this requires further jigs and mounting fixtures. The embrittlement of the cement in combination with the hardening of the pads over a period of time, will cause the premature failure of some of the microphones constructed and assembled in accordance with the above described prior art practices. A variable resistance type of microphone is usually constructed from a plurality of relatively heavy and expensive metal parts which are either die formed from sheet metal material or are machined from solid metal stock.

In view of the above, it is the prime or ultimate object of the present invention to provide a highly improved and highly simplified microphone construction. According to the principles of the present invention great simplification is achieved in the constructon of microphones of both the piezoelectric and variable resistance types through the use of properly formed component parts of improved design. These component parts are formed from resilient and compliant material such as polyethylene, for examplewhich exhibit physical properties of certain resiliency, flexibility, and strength. The inherent physical properties of these materials are fully utilized in the present invention to completely eliminate the need of pads and other like mounting elements which have characterized prior art microphone constructions.

Another object of the invention is to provide an im- 3,007,013 Patented Oct. 31, 1961 proved microphone construction wherein the transducer element is adapted to be resiliently clamped between a pair of snap-fitted component parts and wherein these component parts are adapted to impart the desired degree of damping to the clamped transducer element.

A further object of the invention is to provide improved microphone construction which embodies extremely simplified and highly advantageous terminal pin means for effecting the required electrical contact with the electrodes of the transducer element. The above mentioned Snap-fitted component parts not only resiliently clamp the transducer element but also resiliently press the terminal pin means into tight contacting engagement with the electrodes of the transducer element.

Yet a further object of the invention is the provision of improved microphone construction wherein any of a large number of different types of transducer elements may be employed. Also, the component parts may be used to construct different types of microphonessuch as piezoelectric or variable resistance microphones, for example.

A still further object in the invention is to provide a microphone construction having the characteristics described above which is adapted to be very easily assembled in a highly simplified manner.

The above, as well as other objects and advantages of the present invention, will become more readily apparent upon consideration of the following specification and accompanying drawing wherein there are disclosed certain preferred embodiments constructed in accordance with the objects of the invention.

In the drawing:

FIGURE 1 is a fragmentary plan view of a microphone constructed in accordance with the objects of the present invention;

FIGURE 2 is a fragmentary enlarged side sectional view taken along the section line II-II of FIGURE 1;

FIGURES 3 and 4 are fragmentary plan views, similar to FIGURE 1, depicting the microphone construction of the present invention employing other types of transducer elements; and

FIGURE 5 is an enlarged fragmentary side sectional view showing the transducer means and the supporting parts therefor of a variable resistance type microphone utilizing our improved microphone construction.

Referring now to the drawing, and initially to FIG- URES 1 and 2 thereof wherein there is shown a microphone constructed in accordance with the teachings of the present invention, the reference numeral 10 designates a cup-like housing which is formed by stampingfor example, to provide a flat back portion 11, a peripheral and forwardly extending side wall portion 12 and an outwardly projecting rim-like flange portion 13. The flange portion 13 is used to support the circumferential edge 14 of a generally circular acoustical diaphragm 15. The acoustical diaphragm 15 is formed from a strong and light weight material, such as aluminum or mylar plastic, for example, and its center may be dished inwardly whereby the diaphragm has an overall conical shape. In the center of the flat back portion 11 of the cu -like housing 10 there is provided a circular aperture 16 and an annular recess 17 which encircles the aperture 16 on the rear face of the back portion 11. The annular recess 17 defines an annular and inwardly projecting flange 18 that is disposed about the periphery of the opening 16. Fitted into the opening 16 is a cupshaped supporting member 19 which cooperates with a snap-ring 20, in a manner to be later described, to support a transducer element, generally designated by the reference numeral 21. Both the cup-shaped supporting member 19 and the snap-ring 29 are formed, by molding, for example, from a suitable material, such as one of the newer plastics, having desired physical properties of strength, resiliency, hardness, etc.

The cup-shaped supporting member 19 is provided with a continuous bottom portion 22 that terminates in a radially extending annular flange 23 which is adapted to be nestingly received in the annular recess 17 provided in the flat back portion 11 of the cup-like housing 10. The cup-shaped supporting member 19 has a forwardly projecting tubular body portion 25 which is flat at its upper end 26 and has a downwardly directed hook-like flange 27 that surrounds this upper end 26.

The snap-ring 20 comprises a generally tubular body portion 30 of appreciable length that terminates at its inner end in an inwardly directed locking flange 31 and an outwardly directed annular flange 32. As will hereinafter be more fully explained, the flange 32, bears against the flat back portion 11 of the cup-like housing to provide an air seal while the locking flange 31 is adapted to cooperate with the hook-like flange 27 of the cupshaped supporting member 19 to properly clamp and support the transducer element 21. The outer end of the snap-ring terminates in an inwardly directed clamping flange 33 whose internal diameter conforms generally to the internal diameter of the cup-shaped supporting member 19.

To provide electrical connection with the transducer element 21 there are provided a pair of terminal pins 35 and 36. The terminal pin 35 has a flat T-shaped head 37 and an elongated thin diameter stem 38 while the terminal pin 36 is provided with a flat L-shaped head 39 and an elongated thin diameter stem 40. The terminal pins 35 and 36 are quite similarthe difference between the same being that one has a T-shaped head and the other has a L-shaped head. These terminal pins may be fabricated by flattening the ends of pieces of wire in suitable dies, for example.

The transducer element 21 depicted in FIGURES 1 and 2 of the drawing is of the piezoelectric type and comprises a mass of piezoelectric material 41, preferably ceramic, having current conductive electrodes 42 and 43 on the opposite major surface areas thereof. The terminal pin 35 is used to afford electrical contact with the electrode 42 on the inner surface of the transducer element while the terminal pin 36 provides electrical contact with the electrode 43 on the outer surface of the'transducer element. It will be noted that the lower electrode 42 engages the T-shaped head 37 of the terminal pin 35 while the L-shaped head 39 of the terminal pin 36 overlies. the electrode 43. In order to accommodate the stems 38 and 40 of the terminal pins 35 and 36 a pair of holes, not particularly shown, are drilled or otherwise formed through the entire length of the tubular body portion of the cup-shaped supporting member 19.

In assembling the microphone shown in FIGURES 1 and 2 of the drawings, the cup-shaped supporting member 19 is positioned in the aperture 16 with its flange 23 firmly seated in the annular recess 17. Then the stem 38 of the terminal pin is forced into its respective hole until the T-shaped head 37 rests snugly against the flat and annular upper end 26 of the cup-shaped supporting member 19. The transducer element 21, having a coupling member 45 already attached thereto intermediate its ends, is now positioned in spanning relation across the cup-shaped supporting member 19 whereby its ends are supported by the flat surface 26 of the supporting member. One of the ends of the transducer element 21 overlies the T-shaped headed end 37 of the terminal pin 35 at this time. The stem of the terminal pin 36 is now forced into its respective hole positioned adjacent the otherend of the transducer element 21 so that the L-shaped head 39 presses against the electrode 43 of the transducer element. At this time it should be noted that the electrodes 42 and 43 of the transducer element are in contact with the headed ends 37 and 39 of the terminal pins 35 and 36, respectively.

, through the air.

The snap-ring 20 is now positioned over the cup-shaped supporting member 19 and the transducer element 21, and is pressed down into place so that the locking flange 31 rides down over the hook-like flange 27. As intimated above, both the cup-shaped supporting member 19 and the snap-ring '20 are formed from materials exhibiting de sired physical properties of resiliency whereby upon relative movement of the snap-ring 20 with respect to the cup-shaped supporting member 19 the hook-like flange 27 and the locking flange 31 are deformed. However, when the locking flange 31 passes over the hook-like flange 27, these flanges return to their original shapes and the oppositely disposed and interlocking right angular adjacent portions thereof prevent relative movement or separation of these parts. It will be noted that the lower end of the locking flange 31 and the upper end of the hook-like flange 27 are tapered to facilitate assembly of the cup-shaped supporting member 19 and the snapring 20.

The cup-shaped supporting member '19 and the snapring 20 are so relatively dimensioned that the flange 32 of the snap-ring resiliently bears against the flat back portion 11 of the cup-like housing 10 to securely and rigidly mount these component parts Within the housing. The inwardly directed clamping flange 33 of the snapring 20 presses against the ends of the transducer element and maintains the transducer element in its proper position. This clamping force also maintains the required electrical contact between the terminal pins 35 and 36 and the electrodes 42 and 43 of the transducer element. The resilient engagement between the flange 35 of the snap-ring 20 and the flat back portion 11 of the cup-like housing 10 seals the rear of the assembly against air leakage and this sealing materially assists in determining and controlling the response characteristics of the microphone. Also, the inherent resiliency and compliance of the cup-shaped supporting member 19 and the snap-ring 20 imparts the desired degree of damping to the transducer element.

To complete the assembly of the microphone, the diaphragm 15 is positioned with its circumferential edge 14 overlying the outwardly directed flange portion 13 of the cup-shaped housing 10 and is secured thereto by means of suitable adhesive, not particularly shown. Finally the center of the diaphragm 15 is depressed until the end portion of the coupling member 45 protrudes thereabove and a fillet of cement 46 is applied to maintain the driving connection between the flexible diaphragm 15 and the coupling member 45.

In the use of the microphone above described, the diaphragm 15 is presented to acoustical waves traveling These waves cause the diaphragm to vibrate and such vibrations are transmitted via the coupling member 45 to the middle of the transducer element 21. The transducer element 21 appears as a beam supported at its ends and the mechanical vibrations supplied thereto are impressed at a point intermediate its ends. Such mechanical vibrations are converted by the transducer element into proportional electrical impulses which are collected by the conductive electrodes 42 and 43. These impulses appear across the terminal pins 35 and 36 and quick detachable clips 47 and associated lead wires may be attached to the reanwardly protruding end portions of the terminal pins for conducting such impulses to ancillary electrical equipment, not shown.

The transducer elements employed in the microphone shown in FIGURES =3 and 4 of the drawing are slightly dilferent than the transducer element 21. However, the microphone constructions depicted in FIGURES 3 and 4 are similar to that shown in FIGURES 1 and 2 and to avoid unnecessary repetition in the specification component parts which are common to all embodiments of the invention will not be described again and are indicated by like reference numbers throughout all views of the drawing.

In FIGURE 3 the microphone construction of the present invention is shown supporting a rectangular transducer element 50 by clamping three of its corners while leaving the fourth corner free. This particular microphone employs a torque type of piezoelectric transducer element which may be formed from Rochelle salt, for example. It will be noted that the aperture 16 and the cup-shaped supporting member 19 are located eccentrically and off center with respect to the cup-like housing 10. This allows a coupling member 51 which is attached to the free fourth corner of the transducer element 56' to be positioned along the center axis of the cup-like housing 10 whereby a concentric conical diaphragm 15 may be employed. In this embodiment of the invention one clamped corner of the transducer element 50 overlies the T-shaped head 37 of terminal pin 35 while another clamped corner of the transducer element is engaged by the L-shaped head 39 of terminal pin 36.

FIGURE 4 illustrates the microphone construction of the present invention employed in connection with a square transducer element 55. In this instance three corners of the transducer element are clamped between and by the cup-shaped supporting member 19 and the snap-ring 20 while the fourth corner mounts an upwardly extending coupling member 56. The supporting element 19 and the snap-ring 20 are disposed concentrically with respect to the cup-like housing 10 whereby the driving member 56 is positioned off center with respect to and to one side of the center axis of the cuplike housing. Consequently, an eccentric conical diaphragm 57 must be employed. It should be understood that the transducer element 55 may be eccentrically positioned with respect to the housing 10 if it is desired to employ a concentric diaphragm or, conversely, the transducer element 50 of FIGURE 3 may be mounted concentrically in the housing 10 and an eccentric diaphragm employed.

FIGURE depicts the application of the teachings of the present invention to the construction of a variable resistance type of microphone. In this instance a modified cupshaped supporting element 19 is employed. The supporting element 19' has a hemispherical recess 60 therein whose upper face is coated with a conductive layer 61, such as a dispersion of colloidal graphite, for example. The conductive layer 61 extends about the annular and flat upper end 26 of the supporting member 19. A quantity of graphite granules 62 are located in the hemispherical recess 66* and the T-shaped head 63 of a terminal pin '64 is in electrical contact with the conductive layer 61. An extremely flexible membrane 65, of nylon or mylar plastic, for example, is placed smoothly over the flat upper end 26 of supporting member 19 and is held in place by the snap-ring 20.

A small cap 66 of current conductive metal is secured to the membrane 65 by means of a screw 67. A metallic diaphragm 68 is also held securely on the screw 67 by means of a suitable nut 69. 'Electrical connection to the cap '66 is afforded-through the screw 67, metallic diaphragm 68, and the metallic housing 10. The carbon granules 62 are thus entrapped in the recess 60 between the current conductive cap 66 and the conductive layer 61 and constitute a path of resistance therebetween. Vibrations of the diaphragm 68 will cause the effective resistance of this path to vary, as is well known in the art, to modulate a direct current potential.

It should thus be apparent that we have accomplished the objects initially set forth by providing a highly improved and highly simplified microphone construction. Of particular importance is the manner in which the cupshaped supporting member 19 and the snap-ring 20 cooperate to very securely and resiliently support the transducer element and to hold the various component parts in properly assembled relation. The need of mounting and positioning fixtures and complicated assembly operations of the prior art are completely eliminated and, in accordance with the teachings of the present invention, microphones may be properly assembled by even the most unskilled labor in a minimum of time. Also of importance is the fact that the microphone construction of the present invention is adapted for use in mounting an unlimited number of different types of transducer elements and in providing various types of microphones.

Although We have disclosed certain preferable embodiments of the invention, it should be apparent that many changes may be made therein without departing from the true scope and intent of the invention. Accordingly reference should be had to the following appended claims.

We claim:

1. An improved microphone construction comprising a cup-like housing, a resilient and generally annular supporting member mounted in said housing, a transducer element supported by said supporting member, a resilient snap-ring, means to secure said snap-ring to said supporting member to secure said transducer element between said supporting member and said snap-ring, said transducer having electrode means, terminal pin means contacting said electrode means, a diaphragm, and means interconnecting said diaphragm and said transducer element.

2. Apparatus according to claim 1 further characterized in that said supporting member has an upper end, a hook-like annular flange about the outer periphery of said supporting member adjacent said upper end thereof, said snap-ring being generally annular and having a lower end, an annular locking flange about the inner periphery of said snap-ring adjacent said lower end thereof, and said hook-like flange and said locking flange cooperating to define said means to secure said snap-ring to said supporting member.

3. Apparatus according to claim 2 further characterized in that said transducer element spans and is supported at spaced points on said upper end of said supporting member, said snap-ring having an inwardly directed annular clamping flange adjacent its outer end, and said supporting member and said snap-ring being so relatively dimensioned that said clamping flange resiliently bears against the portion of said transducer element supported on said supporting member when said locking flange and said hook-like flange cooperate.

4. Apparatus according to claim 2 further characterized in that said terminal pin means comprises at least one terminal pin, said terminal pin having a head and a stem, said stern extending through said supporting member, and said head being positioned adjacent said upper end of said supporting member for contacting said electrode means of said transducer element.

5. Apparatus according to claim 2 further characterized in that said cup-like housing has an upwardly extending sidewall, a diaphragm extending across said cup-like housing, said diaphragm being attached at its peripheral edges to said sidewall of said cup-like housing, and said means interconnecting comprising a coupling member extending between said transducer element and said diaphragm.

6. An improved microphone construction comprising a housing, a resilient upwardly extending supporting member mounted in said housing, a transducer element supported by said supporting member, a resilient snap-ring, and means to secure said snap-ring and said supporting member to secure said transducer element between said supporting member and said snap-ring.

7. Apparatus according to claim 6 further characterized in that said supporting member comprises a generally flat annular upper end, said transducer element spanning said supporting member with portion thereof resting on said upper end of said supporting member, said snap-ring having an annular clamping flange adapted to overlie said flat upper end, and supporting element and said snap-ring being so relatively dimensioned that said transducer element is resiliently clamped between said clamping flange of said snap-ring and said upper end of said supporting member.

8. Apparatus according to claim 6 further characterized in that said means to secure comprises a hook-like flange and a locking flange, said locking flange and said hooklike flange being carried by said snap-ring and supporting member, and said flanges cooperating to secure said supporting member and said snap-ring to each other.

9. Apparatus according to claim 8 further characterized in that each of said hook-like and said locking flanges has a tapered portion adjacent one end thereof and a right angular portion adjacent the other end thereof, the tapered portions of said flanges allowing relative passage and deformation of said flanges during assembly of said supporting member and said snap-ring, and the right angular portions of flanges nesting after assembly to prevent separation of said supporting member and said snap-ring.

10. An improved microphone construction comprising a housing, said housing having an aperture therein, a resilient cup-shaped supporting member seated in said opening, said cup-shaped supporting member having an outwardly extending flange engaging the rear outer surface of said housing adjacent said opening, a transducer element supported by said supporting member, a resilient snap-ring, means to secure said snap-ring and said supporting member to each other, said snap-ring having a flange thereon adapted to resiliently bear against the internal surface of said housing adjacent said opening, and said supporting member and said snap-ring being so relatively dimensioned that when the same are assembled said transducer element is clamped between the same, the same are maintained in assembled relation with respect to said housing and said microphone construction is sealed from air leakage from below.

11. Apparatus according to claim 10 further characterized in that said means to secure comprises a hook-like flange and a locking flange, said locking flange and said hook-like flange being carried by said snap-ring and said supporting member, and said last mentioned flanges cooperating to secure said supporting member and said snap-ring to each other.

12. An improved microphone construction comprising a housing, an upstanding supporting member in said housing, a transducer means supported by said supporting member, said transducer means having electrode areas, terminal means contacting said electrode areas, said terminal means comprising at least one terminal pin, said terminal pin having an elongated stem and an enlarged formed head, said stem having a portion extending through said supporting member and a portion projecting from said housing to define an output terminal, said enlarged formed head resting on said supporting member and contacting one of said electrode areas, said enlarged formed head being T-shaped, said terminal means comprising a second terminal pin having a stem and an enlarged L- shaped head, said stem of said second terminal pin having a portion extending through said supporting member and a portion projecting from said housing to define a second output terminal, and said enlarged L-shaped head resting on said supporting member and contacting another of said electrode areas.

13. An improved microphone construction comprising a housing, a resilient supporting member mounted in said housing, said supporting member having a recess therein and a flat and generally annular upper end, said recess and said upper end being coated with a layer of current conductive material, a quantity of carbon granules received in said recess, a current conductive cap in contact with said granules and spaced from said layer, a thin membrane of material overlying said granules and said upper end of said supporting member, a resilient snap-ring, means to secure said snap-ring to said supporting member to resiliently clamp said membrane, and terminal pin means for elfecting electrical connection with said cap and said layer.

References Cited in the file of this patent UNITED STATES PATENTS 1,096,677 Brown May 12, 1914 1,486,132 Egerton Mar. 11, 1924 1,592,059 Wiggins July 13, 1926 1,865,210 Purser June 28, 1932 2,431,022 Brodie Nov. 18, 1947 2,435,920 Burroughs Feb. 10, 1948 2,819,351 Heller Jan. 7, 1958 2,905,771 Burns Sept. 22, 1959 FOREIGN PATENTS 440,330 Great Britain Dec. 23, 1935 

